Method and application of preparing nanocellulose composite film from discarded plant fiber lunch boxes

Abstract

The present invention provides a method for preparing a glyceride-nanocellulose composite film from a discarded plant fiber lunch box, the method being: after rinsing the discarded bamboo fiber lunch box with clean water, putting it into a micro-nano bubble generator, washing it with micro-nano bubbles with a particle size of 100nm-50μm at a rated power of 350W and a water temperature of 20-30°C, drying it, cutting it into pieces, crushing it, and sieving it to obtain a plant fiber powder; mixing the plant fiber powder, glyceride and pure water, stirring and breaking the wall for 2min, obtaining a glyceride-plant fiber slurry, grinding it, obtaining a nanocellulose gel liquid, putting it into an aluminum tray and drying it, and obtaining a glyceride-nanocellulose composite film. Applications are also provided for packaging materials. The glyceride-nanocellulose composite film prepared by the present invention has good light transmittance and thermal stability, providing space for performance optimization for packaging materials.

Description

Technical Field

[0001] The invention belongs to the technical field of plant fibers, and specifically relates to a method for preparing a glyceride-nanocellulose composite film from waste plant fiber lunch boxes and application thereof. Background Art

[0002] Film packaging is highly dependent on petroleum-based plastics. With the growth of packaging product consumption and the rapid shortening of their life cycle, the non-renewable and non-degradable nature of raw materials has brought great troubles to the use of plastics. Transparent paper is made of natural cellulose fibers, which have many advantages such as high transparency, mechanical flexibility, high strength and heat resistance. More importantly, it can be naturally degraded without causing environmental problems. However, the traditional bottom-up nanocellulose preparation method is inefficient, costly and environmentally unfriendly, making it difficult to carry out large-scale applications.

[0003] Nanopaper is traditionally manufactured through a bottom-up approach, which mainly includes two steps: mechanical or chemical decomposition of cellulose nanofibers from wood; and formation of cellulose nanofiber networks through different manufacturing techniques. The fibrillation of nanocellulose requires strong shear forces, with energy consumption ranging from 1550 to 21000 KWh / ton. The energy consumption required to separate nanocellulose from plant fibers depends largely on its chemical composition, cell morphology and cell wall ultrastructural organization. During the growth of trees / bamboo, a large amount of lignin is synthesized and deposited in the corners of macrofibers and parenchyma cells, forming a tightly bound interface through many covalent bonds and hydrogen bonds. Plant fibers with high lignin content and compact cell wall structure are more resistant to fibrillation. As a fully delignified and fiber-separated material, waste plant fiber lunch boxes require fewer processing steps for the preparation of nanocellulose. This strategy also provides a new channel for the high-value-added secondary utilization of waste bamboo fiber lunch boxes, which are currently mainly landfilled and incinerated (>90%). Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method and application of preparing glyceride-nanocellulose composite film from waste plant fiber lunch boxes in view of the shortcomings of the above-mentioned prior art. The glyceride-nanocellulose composite film prepared by this method has good light transmittance and thermal stability, providing room for performance optimization of packaging materials.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a glyceride-nanocellulose composite film from waste plant fiber lunch boxes, the method comprising:

[0006] S1. After rinsing the discarded bamboo fiber lunch box with clean water, put it into a micro-nano bubble generator, wash it with micro-nano bubbles with a particle size of 100nm to 50μm for 5h to 10h at a rated power of 350W and a water temperature of 20℃ to 30℃, take it out and dry it to obtain a washed bamboo fiber lunch box;

[0007] S2, cutting the washed bamboo fiber lunch box obtained in S1 into pieces, and then crushing them in a grinder with a rotation speed of 32000 rpm and a rated power of 900 W, and sieving them to obtain plant fiber powder;

[0008] S3, after mixing the plant fiber powder, glyceride and pure water obtained in S2, putting them into a wall breaking machine, stirring and breaking the wall at 37000r / min for 2min, to obtain a glyceride-plant fiber slurry;

[0009] Glycerol esters are mixed with plant fibers to prepare nanocellulose. Since the refractive index of glycerol esters (1.47) is similar to that of plant fibers (1.53), the refraction and reflection of light are reduced, and the light transmittance of the cast film is higher. Secondly, glycerol esters have high thermal stability, and the maximum thermal weight loss temperature of the composite film moves toward high temperature.

[0010] S4, grinding the glyceride-plant fiber slurry obtained in S3 in a grinder with a grinding disc spacing of 300 μm and a grinding disc speed of 1500 rpm for 3 times, each time for 5 min to 10 min, to obtain a nanocellulose gel solution. The high-speed grinding preparation method is simple to operate, easy to clean, and has a low concentration requirement for the initial slurry;

[0011] S5. Put the nanocellulose gel solution obtained in S4 into an aluminum plate, and dry it at 40° C. for 24 h to 30 h to obtain a glyceride-nanocellulose composite film.

[0012] Preferably, the mass fraction of the plant fiber in the washed bamboo fiber lunch box in S1 is 85% to 90%.

[0013] Preferably, the mesh size of the sieving in S2 is 150-300 meshes.

[0014] Preferably, the usage ratio of the plant fiber powder, glyceride and pure water in S3 is 5g: (0.25-0.35) mg: 995 mL.

[0015] Preferably, the diameter of cellulose in the nanocellulose gel solution in S4 is 50 nm to 100 nm.

[0016] Preferably, the thickness of the glyceride-nanocellulose composite film in S5 is 30 μm to 50 μm.

[0017] Preferably, the pyrolysis temperature of the glyceride-nanocellulose composite membrane in S5 is 371.6° C. to 375° C., and the transmittance of the glyceride-nanocellulose composite membrane at 600 nm is 76.2% to 78.6%.

[0018] The present invention also provides the use of the waste plant fiber lunch box prepared by the above method to prepare a glyceride-nanocellulose composite film, and the glyceride-nanocellulose composite film prepared by the waste plant fiber lunch box is used as a packaging material.

[0019] The film prepared by the present invention has good light transmittance and thermal properties. The good light transmittance, when made into food packaging materials, is convenient for customers to identify and purchase, and can reflect the beauty of food; the good thermal stability can ensure that the film does not change in size when heated, and the surface does not shrink or deform, etc., which has an important influence on the aesthetics of flexible packaging.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. The method for preparing a glyceride-cellulose composite film using discarded bamboo fiber lunch boxes of the present invention eliminates the need for separating fibers and delignifying from wood, and eliminates the steps of pulping and delignifying in the fibrillation process, which has the effects of high yield, low production cost and chemical waste; micro-nano bubbles are used to remove food solution remaining in the plant fiber lunch box, which provides cheap and high-quality raw materials for the preparation of nanocellulose; the present invention mixes plant fiber powder, glyceride and pure water to prepare a glyceride-plant fiber slurry, and the cast film has high light transmittance and thermal stability, and then high-speed grinding is performed to obtain a nanocellulose gel liquid. The high-speed grinding preparation method is simple to operate, easy to clean, and has low requirements on the concentration of the initial slurry; the composite film prepared by the high-speed grinding has the advantages of high transparency and strong thermal stability, which provides room for performance optimization for packaging materials.

[0022] The present invention is further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a picture of the glyceride-nanocellulose composite film prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0024] Example 1

[0025] The method for preparing a glyceride-nanocellulose composite film from waste plant fiber lunch boxes in this embodiment is as follows:

[0026] S1. After rinsing the discarded bamboo fiber lunch box with clean water, put it into a micro-nano bubble generator, wash it with micro-nano bubbles with a particle size of 50 μm for 10 hours at a rated power of 350 W and a water temperature of 25° C., take it out and dry it to obtain a washed bamboo fiber lunch box; the mass fraction of plant fiber in the washed bamboo fiber lunch box is 88%;

[0027] The model of the micro-nano bubble generator in this embodiment is JXWNP-AL01, which was purchased from Shanghai Zhongchen Digital Technology Equipment Co., Ltd.;

[0028] S2, cutting the washed bamboo fiber lunch box obtained in S1 into pieces, and then crushing them in a grinder with a rotation speed of 32000 rpm and a rated power of 900 W, and passing them through a 150-mesh sieve to obtain plant fiber powder;

[0029] S3, after mixing the plant fiber powder, glyceride and pure water obtained in S2, putting them into a wall breaking machine (PB10M2-165E, Midea, China), stirring and breaking the wall in the fruit and vegetable mode (37000r / min) for 2min, to obtain glyceride-plant fiber slurry; the amount ratio of the plant fiber powder, glyceride and pure water is 5g:0.3mg:995mL;

[0030] Glycerol esters are mixed with plant fibers to prepare nanocellulose. Since the refractive index of glycerol esters (1.47) is similar to that of plant fibers (1.53), the refraction and reflection of light are reduced, and the light transmittance of the cast film is higher. Secondly, glycerol esters have high thermal stability, and the maximum thermal weight loss temperature of the composite film moves toward high temperature.

[0031] S4, grinding the glyceride-plant fiber slurry obtained in S3 in a grinder with a grinding disc spacing of 300 μm and a grinding disc speed of 1500 rpm for 3 times, each time for 5 minutes, to obtain a nanocellulose gel solution; the diameter of cellulose in the nanocellulose gel solution is 50 nm to 100 nm;

[0032] S5. Put the nanocellulose gel solution obtained in S4 into an aluminum plate, and dry it at 40° C. for 28 h to obtain a glyceride-nanocellulose composite film with a thickness of 40 μm.

[0033] The glyceride-nanocellulose composite membrane prepared in this example is as follows Figure 1 shown.

[0034] Example 2

[0035] The method for preparing a glyceride-nanocellulose composite film from waste plant fiber lunch boxes in this embodiment is as follows:

[0036] S1. After rinsing the discarded bamboo fiber lunch box with clean water, put it into a micro-nano bubble generator, wash it with micro-nano bubbles with a particle size of 100 nm for 5 hours at a rated power of 350 W and a water temperature of 20° C., take it out and dry it to obtain a washed bamboo fiber lunch box; the mass fraction of plant fiber in the washed bamboo fiber lunch box is 90%;

[0037] The model of the micro-nano bubble generator in this embodiment is JXWNP-AL01, which was purchased from Shanghai Zhongchen Digital Technology Equipment Co., Ltd.;

[0038] S2, cutting the washed bamboo fiber lunch box obtained in S1 into pieces, and then crushing them in a grinder with a rotation speed of 32000 rpm and a rated power of 900 W, and passing through a 300-mesh sieve to obtain plant fiber powder;

[0039] S3, after mixing the plant fiber powder, glyceride and pure water obtained in S2, put them into a wall breaking machine (PB10M2-165E, Midea, China), stir and break the wall in the fruit and vegetable mode (37000r / min) for 2min to obtain glyceride-plant fiber slurry; the amount ratio of the plant fiber powder, glyceride and pure water is 5g:0.25mg:995mL;

[0040] The model of the wall-breaking machine in this embodiment is PB10M2-165E, purchased from Midea, Guangdong, China;

[0041] S4, grinding the glyceride-plant fiber slurry obtained in S3 in a grinder with a grinding disc spacing of 300 μm and a grinding disc speed of 1500 rpm for 3 times, each time for 10 min, to obtain a nanocellulose gel solution; the diameter of cellulose in the nanocellulose gel solution is 50 nm to 100 nm;

[0042] S5. Put the nanocellulose gel solution obtained in S4 into an aluminum plate, and dry it at 40° C. for 24 hours to obtain a glyceride-nanocellulose composite film with a thickness of 50 μm.

[0043] Example 3

[0044] The method for preparing a glyceride-nanocellulose composite film from waste plant fiber lunch boxes in this embodiment is as follows:

[0045] S1. After rinsing the discarded bamboo fiber lunch box with clean water, put it into a micro-nano bubble generator, wash it with micro-nano bubbles with a particle size of 10 μm for 8 hours at a rated power of 350 W and a water temperature of 30° C., take it out and dry it to obtain a washed bamboo fiber lunch box; the mass fraction of plant fiber in the washed bamboo fiber lunch box is 85%;

[0046] The model of the micro-nano bubble generator in this embodiment is JXWNP-AL01, purchased from Shanghai Zhongchen;

[0047] S2, cutting the washed bamboo fiber lunch box obtained in S1 into pieces, and then crushing them in a grinder with a rotation speed of 32000 rpm and a rated power of 900 W, and passing them through a 150-mesh sieve to obtain plant fiber powder;

[0048] S3, after mixing the plant fiber powder, glyceride and pure water obtained in S2, put them into a wall breaking machine (PB10M2-165E, Midea, China), stir and break the wall in the fruit and vegetable mode (37000r / min) for 2min to obtain glyceride-plant fiber slurry; the amount ratio of the plant fiber powder, glyceride and pure water is 5g:0.35mg:995mL;

[0049] S4, grinding the glyceride-plant fiber slurry obtained in S3 in a grinder with a grinding disc spacing of 300 μm and a grinding disc speed of 1500 rpm for 3 times, each time for 8 minutes, to obtain a nanocellulose gel solution; the diameter of cellulose in the nanocellulose gel solution is 50 nm to 100 nm;

[0050] S5. Put the nanocellulose gel solution obtained in S4 into an aluminum plate, and dry it at 40° C. for 30 h to obtain a glyceride-nanocellulose composite film with a thickness of 30 μm.

[0051] Comparative Example 1

[0052] The preparation method of the nanocellulose film of this comparative example is:

[0053] S1. After rinsing the bamboo fiber lunch box with clean water, put it into a micro-nano bubble generator, wash it with micro-nano bubbles with a particle size of 50 μm for 10 hours at a rated power of 350 W and a water temperature of 25° C., take it out and dry it to obtain a washed bamboo fiber lunch box; the mass fraction of plant fiber in the washed bamboo fiber lunch box is 88%;

[0054] S2, cutting the washed bamboo fiber lunch box obtained in S1 into pieces, and then crushing them in a grinder with a rotation speed of 32000 rpm and a rated power of 900 W, and passing them through a 150-mesh sieve to obtain plant fiber powder;

[0055] S3, after mixing the plant fiber powder obtained in S2 and pure water, put it into a wall breaking machine (PB10M2-165E, Midea, China), stir and break the wall in the fruit and vegetable mode (37000r / min) for 2min to obtain plant fiber slurry; the amount ratio of the plant fiber powder to pure water is 5g:0.3mg:995mL;

[0056] S4, grinding the plant fiber slurry obtained in S3 in a grinder with a grinding disc spacing of 300 μm and a grinding disc speed of 1500 rpm for 3 times, each time for 5 minutes, to obtain a nanocellulose gel solution; the diameter of cellulose in the nanocellulose gel solution is 50 nm to 100 nm;

[0057] S5. Put the nanocellulose gel solution obtained in S4 into an aluminum plate, and dry it at 40° C. for 28 h to obtain a nanocellulose film with a thickness of 40 μm.

[0058] The transmittance and maximum pyrolysis temperature of the glyceride-nanocellulose composite membranes prepared in Examples 1-3 and the nanocellulose membrane prepared in Comparative Example 1 were tested. The transmittance was measured using a Lambda 650SUV-vis spectrometer at a wavelength range of 250 to 800 nm, and the pyrolysis temperature was measured using a TATGA55 thermogravimetric device at a nitrogen flow rate of 60 mL / min, a temperature range of 25°C to 800°C, and a heating rate of 20°C / min. The test results are shown in Table 1.

[0059] project Example 1 Example 2 Example 3 Comparative Example 1 600nm transmittance (%) 78.1 76.2 78.6 56.8 Maximum pyrolysis temperature (℃) 373.8 371.6 375 362

[0060] As shown in Table 1, the addition of glyceride improves the transmittance of the glyceride-glyceride-nanocellulose composite film and moves the maximum pyrolysis temperature toward high temperature. The glyceride-nanocellulose composite film prepared by the present invention has good transmittance and high maximum pyrolysis temperature and can be used for high-end food packaging.

[0061] The glyceride-nanocellulose composite film prepared by the method of Examples 1-3 is used as a packaging material.

[0062] The film prepared by the present invention has good light transmittance and thermal properties. The good light transmittance, when made into food packaging materials, is convenient for customers to identify and purchase, and can reflect the beauty of food; the good thermal stability can ensure that the film does not change in size when heated, and the surface does not shrink or deform, etc., which has an important influence on the aesthetics of flexible packaging.

[0063] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a glyceride-nanocellulose composite film from discarded plant fiber lunch boxes, characterized in that: The method is: S1. After rinsing the discarded bamboo fiber lunch box with clean water, put it into a micro-nano bubble generator, wash it with micro-nano bubbles with a particle size of 100nm~50μm for 5h~10h at a rated power of 350W and a water temperature of 20℃~30℃, take it out and dry it to obtain a washed bamboo fiber lunch box; the mass fraction of plant fiber in the washed bamboo fiber lunch box in S1 is 85%~90%; S2, cutting the washed bamboo fiber lunch box obtained in S1 into pieces, and then crushing them in a grinder with a rotation speed of 32000 rpm and a rated power of 900 W, and sieving them to obtain plant fiber powder; the mesh number of the sieving in S2 is 150 mesh to 300 mesh; S3, after mixing the plant fiber powder, glyceride and pure water obtained in S2, put them into a wall breaking machine, stir and break the wall at a speed of 37000r / min for 2min, and obtain glyceride-plant fiber slurry; the amount ratio of the plant fiber powder, glyceride and pure water in S3 is 5g: (0.25~0.35)mg: 995mL; the refractive index of the glyceride is 1.47; S4, grinding the glyceride-plant fiber slurry obtained in S3 in a grinder with a grinding disc spacing of 300 μm and a grinding disc speed of 1500 rpm for 3 times, each time for 5 min to 10 min, to obtain a nanocellulose gel solution; the diameter of cellulose in the nanocellulose gel solution in S4 is 50 nm to 100 nm; S5. Put the nanocellulose gel liquid obtained in S4 into an aluminum plate, and dry it at 40°C for 24h to 30h to obtain a glyceride-nanocellulose composite film; the thickness of the glyceride-nanocellulose composite film in S5 is 30μm to 50μm; the pyrolysis temperature of the glyceride-nanocellulose composite film in S5 is 371.6°C to 375°C, and the transmittance of the glyceride-nanocellulose composite film at 600nm is 76.2% to 78.6%; the glyceride-nanocellulose composite film prepared from the waste plant fiber lunch box is used as a packaging material.

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